Universal tapping arrangement for potentiometers



Dec. 8, 1959 K. c. STREETER 2,916,716

UNIVERSAL TAPPING ARRANGEMENT FOR POTENTIOMETERS Filed Jan. 17, 958

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the use of special tools.

United States Patent TAPPI'NG FOR POTENTIOMETERS Kenneth C. Streeter, Falls Church, Va., assignor to the United States of America as represented by the Secretary of the Air Force Application January 17, 1958, Serial No. 709,717

1 Claim. (Cl. 338-137) desired function.

Heretofore it has been the practice to affix the taps as required for each particular function generator during the manufacturing process. Since each function generator is unique, this requires individual engineering of each potentiometer and results in increased manufacturing costs. This method also makes it necessary, in providing spare parts for equipment using a large number of function generators, to stock replacements for each particular function generator used.

The purpose of the invention is to provide a single basic linear potentiometer design having a universal tap ping arrangement so that taps. in the desired number and at the desired positions can be installed either by the manufacturer or the user in a simple manner and without This permits the manufacture of a single basic potentiometer rather than a number of special designs with different tap arrangements. The spare part problem is also simplified since it is necessary to stock only the basic potentiometer which can easily be fitted with taps to meet the particular requirement by maintenance personnel.

Briefly, in accordance with the invention a standard linear potentiometer is fitted with a tap support member or ring situated near and parallel to the linear resistance element. The tap support member is made of insulating material and is arranged to support an insertable resilient tap element in contact with the resistance element at any of a plurality of closely spaced points along the support member.- The tap elements are made to have a press fit in the support member so that they may be inserted in place by hand or a simple tool. Because of the large number of tap positions provided, taps may be inserted at any points desired along the resistance element. Terminals extending through the potentiometer housing are provided for making electrical connection to the tap elements.

The invention will be described in more detail in conjunction with a specific embodiment thereof shown in the accompanying drawings, in which- Fig. 1 is the schematic equivalent circuit of the function generator shown in Figs. 2 and 3;

Fig. 2 is a plan view of a standard potentiometer with tapping ring in accordance with the invention; and

Fig. 3 is a sectional elevation of Fig. 2.

Referring to Fig. 1, 1 represents the linear resistance ,element of a potentiometer, 2 and 3 represent the terof this element, 4 represents the potentiometer .ments, these taps being connected to terminals 12'17,

respectively. Resistors R1R7 are connected between adjacent pairs of terminals. The positions of the taps and the values of R R are chosen so as to give the desired resistance variation between terminals 3 and 5 as a function of the position of sliding contact 4.

Referring to Figs. 2 and 3, the cover 18 shown in Fig. 3 being removed in Fig. 2, the potentiometer housing 19 contains the linear resistance element 21 positioned against its wall and insulated therefrom by insulating strip 21. Shaft 22 is rotatably supported in housing 19 and has arm 23 clamped to one end over insulating sleeve 24. The arm is raised to its proper position relative to the resistance element of the potentiometer by means of insulating spacer and slip ring support 25. The shaft is retained in the housing by snap ring 26.

The sliding contact 4 is attached by spring member 27 to arm 23. The spring member continues to form two brushes 28 and 29 which cooperate with slip ring 30 to connect the sliding contact to terminal 5, located beneath terminal 2 in Fig. 2, through connecting ribbon 31. Terminals 2, 3 and 5, as well as terminals 1217, may, for example, be supported by an insulating member 32 surrounding the potentiometer housing.

In accordance with the invention, there is provided a tap support member or ring 33 made of insulating material and having a plurality of holes at an angle to the upper face for receiving and holding tap elements such as those numbered 611 in the drawing. These holes may be spaced, for example, at 5 intervals and the location in degrees may be stamped on the ring, as shown in the drawing, in order to facilitate the specification of tap locations. The taps are made of spring metal preferably silver plated for good contact with the resistance element. They should have a snug press fit in the holes of the support member 33 into which they may be inserted by hand or by a simple tool such as small pliers. After insertion the taps are rotated into contact with the resistance element, the inclination of the hole and the spring force exerted by the tap then serving to lock the tap in place.

External feed-through terminals may be provided for making external electrical connections to the taps. Six such terminals, numbered 12-17 are provided in the em bodiment shown in the drawing making this design suitable for any number of taps up to six. Connections between the terminals and taps are made by short flexible wires soldered to both. Resistors R1'R7 are connected between adjacent pairs of these terminals. In some instances it is possible to locate the resistor elements inside the potentiometer housing where they can be soldered directly to the taps thus dispensing with the terminals altogether.

I claim:

A potentiometer having a circular linear resistance element, a sliding contact associated with said resistance element, a tap support ring of insulating material situated within said circular resistance element and concentric therewith, said tap support ring having a plurality of comparatively deep closely spaced cylindrical holes arranged opposite equally spaced points along said resistance element and each adapted to receive a closely fitting insertable tap element, the axes of said holes lying in radial planes relative to said resistance element and making an angle of approximately forty-five degrees with the surface of said resistance element, and an insertable substantially S-shaped tap element made of conductive spring wire in at least one of said holes and in contact with said resistance element.

(References on following page) 3 References Cited in the file of this patent 2,606,984 2,619,570 UNITED STATES PATENTS 2,861,157 2,122,370 Harrison ..June28, 1938 2,270,166 Hiensch Jan. 13,- 1942 5 2,286,029 Van Beuren June 9, 1942 129,906 2,440,906 Metzger May 4; 1948 642,314

Burgess Aug. 12, 1952 Takats Nov. 25, 1952 Chapple Nov. 18, 1958 FOREIGN PATENTS Australia Nov. 9, 1948 Great Britain Aug. 30, 1950 

